Factor V Leiden
One copy of the Factor V Leiden variant detected (heterozygous).
You have one copy of the Factor V Leiden DNA change.
Associated with a roughly 4–7× increased lifetime risk of venous thromboembolism (deep vein thrombosis or pulmonary embolism), though most heterozygotes never experience an event.
Your lifetime risk of a dangerous blood clot (in a deep vein or in the lungs) is roughly 4 to 7 times the average. Even so, most people with one copy never actually have a clot.
What this means
Factor V Leiden is a single-letter change in the F5 gene (R506Q) that makes clotting factor V resistant to inactivation by activated protein C. The result is a slow "leaning forward" of the clotting cascade. It is the most common inherited clotting disorder among people of European ancestry. Carrying the variant doesn't mean a clot is inevitable — the lifetime risk of venous thromboembolism for a heterozygote without other risk factors is still well under one in ten.
Factor V Leiden is a single-letter change in the F5 gene that makes one of your clotting proteins harder for your body to switch off. The result is a clotting system that's slightly "leaning forward" all the time. It's the most common inherited clotting condition in people of European ancestry. Having this DNA change doesn't mean a clot is inevitable — for someone with one copy and no other risk factors, the lifetime chance of a clot is still well under one in ten.
Caveats
- Most carriers go through life without a clotting event.
- Risk is strongly modified by surgery, prolonged immobility, hormonal contraceptives, pregnancy, and smoking.
- Anticoagulation is not routinely recommended for asymptomatic carriers.
- The clinical impact is much larger when combined with the prothrombin G20210A variant.
Populations
- Most common in European-descent populations (about 5% allele frequency); rare elsewhere